24 citations · 44 across the 4 of their papers we have counts for
6 papers · 1 filter
A NICMOS Direct Imaging Search for Giant Planets around the Single White Dwarfs in the Hyades
S. Friedrich, H. Zinnecker, W. Brandner +2
We report preliminary results from our search for massive giant planets (6-12 Jupiter masses) around the known seven single white dwarfs in the Hyades cluster at sub-arcsec separat…
Do Magnetic Fields Prevent Hydrogen from Accreting onto Cool Metal-line White Dwarf Stars?
S. Friedrich, S. Jordan, D. Koester
It is generally assumed that metals detected in the spectra of a few cool white dwarfs cannot be of primordial origin and must be accreted from the interstellar medium. However, th…
Discovery of magnetic fields in hot subdwarfs
S. J. O'Toole, S. Jordan, S. Friedrich +1
We present initial results of a project to measure mean longitudinal magnetic fields in a group of sdB/OB/O stars. The project was inspired by the discovery of three super-metal-ri…
Do weak magnetic fields prevent hydrogen from accreting onto metal-line white dwarf stars?
Susanne Friedrich, Stefan Jordan, Detlev Koester
The widely accepted assumption is that metals detected in the spectra of a few cool helium-rich white dwarfs cannot be of primordial origin and therefore must be accreted from the…
Cool helium-rich white dwarfs from the Hamburg/ESO Survey
S. Friedrich, D. Koester, N. Christlieb +2
We present an analysis of 40 cool helium-rich white dwarfs found in the Hamburg/ESO survey. They were selected for follow-up spectroscopy because of their U-B colour below -0.18, t…
The Seyfert Galaxy NGC 6814 -- a highly variable X-ray source
Michael Koenig, Susanne Friedrich, Ruediger Staubert +1
The Seyfert galaxy NGC 6814 is a highly variable X-ray source despite the fact that it has recently been shown not to be the source of periodic variability. The 1.5 year monitoring…